Such sensors are disclosed by way of example in DE 197 53 805 C2 and in the brochure “Temposonics Position Sensors”, 551019 A of the company MTS (www.mtssensors.com/fileadmin/media/pdfs/551019.pdf) and are in particular used in industrial metrology to measure positions, lengths or covered distances. The waveguide can be a thin bar, a wire or a pipe of a ferromagnetic material such as iron, nickel or cobalt which can have a length of a few centimeters up to a plurality of meters, for example. A so-called “position magnet”, for example in the form of a permanent magnet, which generates a magnetic field in the waveguide is typically attached to the component whose position should be detected. The position magnet can, for example, be of ring shape and surround the waveguide. If an electrical current pulse is sent through the waveguide, a further magnetic field which is variable with respect to time and place is generated in the environment of the waveguide in addition to the magnetic field generated by the position magnet. Due to the interaction of the two magnetic fields at the site of the position magnet, a mechanical pulse such as a longitudinal pulse and/or a torsion pulse can be generated in the waveguide and moves along the measurement path. A transducer of the position sensor typically serves to convert the mechanical pulses conducted by the waveguide into position signals. The transducer can, for example, comprise a coil or a piezoelectric measurement element. The transducer can, for example, be designed as described in EP 0 882 212 B1. The position of the position magnet can ultimately be determined by a measurement of the travel time of the mechanical pulse. Position sensors based on the magnetostrictive measurement principle work in a contactless manner and supply absolute values. They do not require a recalibration and they are also suitable for adverse conditions of use. They are frequently configured as linear path sensors.
Since position sensors of the named kind should often be used in rough environments, for example in pressurized hydraulic cylinders, the housing for the waveguide has to be relatively stable and resistant. The measurement path is generally relatively long, typically over one meter. This means that the thin waveguide has to be introduced into and centered in the housing over such a large path.
In known systems, the waveguide is jacketed by an acrylic pipe or by a fiber glass pipe which is arranged in the housing. Unavoidable gaps between the waveguide and the jacket as well as between the jacket and the housing have the result that the waveguide moves during the operation and is decentered in the process. In addition, it has been shown in practice that the jackets do not provide sufficient protection against shocks and vibrations. A kinking or a jamming of the waveguide may occur on the introduction of a waveguide into an acrylic pipe or fiber glass pipe having a length of one or more meters.
A position sensor is disclosed in DE 197 53 805 C2 in which the waveguide is supported in a support of insulating material. A pressing sleeve is pressed onto the axial end region of the waveguide together with the insulating material on the assembly.
WO 2016/128021 A1 discloses a magnetostrictive path measurement apparatus in which the waveguide is supported in an elastic support hose which is in turn arranged in a support pipe.
Magnetostrictive path measurement apparatus having elastic support elements are also disclosed in US 2004/0090225 A1, in US 2001/0017539 A1 and in U.S. Pat. No. 6,401,883 B1.